Machines such as vehicles, either self-propelled or pushed or pulled, often include wheels for facilitating travel across terrain. Such wheels often include a tire to protect a rim or hub of the wheel, provide cushioning for improved comfort or protection of passengers or cargo, and provide enhanced traction via a tread of the tire. Pneumatic tires are an example of such tires. Pneumatic tires include an enclosed cavity for retaining pressurized air, with the enclosed cavity being formed by either a separate annular tube or by a sealed coupling between the tire and a rim of the hub. By virtue of the pressurized air, the tire provides cushioning and shock absorption as the wheel rolls across terrain.
Pneumatic tires, however, may suffer from a number of possible drawbacks. For example, pneumatic tires may deflate due to punctures or air leaks, rendering them unsuitable for use until they are repaired or replaced. In addition, pneumatic tires may be relatively complex due to separate tubes or complex configurations for providing a sealed coupling between the tire and the rim.
In addition to these drawbacks, pneumatic tires may suffer from a number of economic drawbacks. For example, due to the relatively complex nature of pneumatic tires, manufacturing facilities for pneumatic tires may be prohibitively costly, requiring a large capital investment. Moreover, pneumatic tires formed from natural rubber may be susceptible to dramatic variability in production costs due to inconsistent availability of natural rubber.
Non-pneumatic tires, such as solid tires or tires not retaining pressurized air, may provide an alternative to pneumatic tires. Non-pneumatic tires may be relatively less complex than pneumatic tires because they do not retain air under pressure. However, non-pneumatic tires may suffer from a number of possible drawbacks. For example, non-pneumatic tires may be relatively heavy, and may not have a sufficient ability to provide a desired level of cushioning. For example, some non-pneumatic tires may provide little, if any, cushioning, potentially resulting in discomfort to passengers and/or damage to cargo and/or the machine on which the tires are installed. In addition, some non-pneumatic tires may not be able to maintain a desired level of cushioning when the load changes on the tire. In particular, if the structure of the non-pneumatic tire provides the desired level of cushioning for a given load, it may not be able to continue to provide the desired level of cushioning if the load is changed. For example, if the load is increased, the structure of the non-pneumatic tire may collapse, resulting in a loss of the desired level of cushioning or potentially damaging the tire. If the load is decreased, the level of cushioning may also decrease, resulting in an undesirable reduction in comfort and/or protection. In addition, conventional non-pneumatic tires that provide adequate cushioning may not be able to maintain the desired machine height when loaded, due to collapse of the tire under load.
An example of a cushioned tire that is not inflated is disclosed in U.S. Pat. No. 2,620,844 to Lord (“the '844 patent”). In particular, the '844 patent discloses a cushioned tire formed from a resilient material such as rubber. The tire includes a rigid inner rim shaped to be mounted on a wheel, an outer continuous tread section formed of resilient material such as rubber, and a cushion formed of resilient material extending between and connected to or united with the rim and tread section. The cushion of the tire is provided by openings that extend from one side to the other of the tire and are formed by walls which extend around the tire, with the walls being formed to transmit loads that act radially between the rim and tread.
Although the cushioned tire disclosed in the '844 patent provides an alternative to pneumatic tires, it may suffer from a number of drawbacks associated with non-pneumatic tires. For example, the tire disclosed in the '844 patent may not be able to maintain a desired level of cushioning when the load on the tire changes.
In addition, some non-pneumatic tires may be unusually large, rendering it difficult to form the tire via molding. For example, some very large machines may require unusually large tires, and forming such a large tire may present technical difficulties due to the volume of material required to form the tire. For example, forming a non-pneumatic tire by molding the tire may be difficult due to problems associated with obtaining relatively uniform temperature, heating rates, and/or cooling rates throughout such a large volume of material. In addition, it may be difficult to form a tire via molding where the molded tire has a complex structure.
The systems and methods for forming non-pneumatic tires disclosed may be directed to mitigating or overcoming one or more of the possible technical difficulties set forth above.